This invention relates to an apparatus for sputter etching a substrate such as a silicon substrate or the like.
A previously known apparatus is shown in FIG. 1, for instance. A vacuum treatment chamber a has a sputter etching electrode c supporting a substrate b. The electrode c is applied with DC power or RF electric power from an electric power source d to generate a plasma e in front thereof. Ions contained in the plasma e may impinge on the substrate b to etch the same.
This type of apparatus, however, is defective in that a sufficiently high plasma concentration cannot be obtained because the plasma e is diffused ahead of the electrode c. Consequently, the etching rate, that is, an etching depth per unit time becomes low.
As for a means for heightening the plasma concentration, the application of the electric power can be increased to the electrode c. This, however, is counterproductive in that if the electric voltage of the electrode c is increased, the energy of the ions impinging on the substrate b also becomes high. Consequently, damage to a pattern to be formed on the substrate b or a lowering in characteristics of the pattern are liable to occur. Such difficulties are especially liable to occur with respect to a thin or brittle substrate or a sensitive element such as LS1, a VLSI or the like. In addition, in a case where the substrate b is made of silicon and is sputter etched by Ar ions, innumerable fine injuries on account of lattice defects thereof are given to the surface of the treated substrate. Such fine injuries deteriorate the electrical characteristics of such a product as a fine pattern of a VLSI element or the like, and cause a hindrance to making a more fine pattern.